Bootstrap vs Primer


Choosing the right CSS framework can significantly impact the development process and outcome of web projects. Two popular CSS frameworks that often come up in discussions are Bootstrap and Primer. Both frameworks offer a range of features that cater to different needs, but how do they compare? This comprehensive article aims to dissect the similarities and differences between Bootstrap and Primer, helping you make an informed decision on which framework best suits your project needs.

What is Bootstrap?

Bootstrap is a widely-used open-source CSS framework that also includes JavaScript components. It was created by Twitter developers Mark Otto and Jacob Thornton to encourage consistency across internal tools. Today, Bootstrap is known for its responsive grid system, pre-designed components, and powerful plugins.

Popular Add-ons for Bootstrap

  • BootstrapVue: BootstrapVue provides one of the most comprehensive implementations of Bootstrap components for Vue.js.
  • React-Bootstrap: React-Bootstrap replaces the Bootstrap JavaScript with React components.
  • Bootswatch: Bootswatch offers free themes for Bootstrap.

What is Primer?

Primer is GitHub’s open-source CSS framework that powers its interface design. It’s built with an emphasis on GitHub’s design principles and provides a more refined and constrained set of styling options compared to Bootstrap. Primer is known for its system of variables, utilities, and components that are designed to work harmoniously together.

Popular Add-ons for Primer

  • Octicons: Octicons are GitHub’s icon set, designed to be used with Primer.
  • Primer Components: Primer Components is a React implementation of Primer’s design system.

Comparison of Features

Grid System and Responsiveness


Bootstrap’s grid system is based on a 12-column layout and uses a series of containers, rows, and columns to layout and align content. It’s built with flexbox and allows almost any layout design to be realized. Responsive breakpoints are also an integral part of Bootstrap’s grid, making it easy to create designs that work on all devices.

<div class="container">
  <div class="row">
    <div class="col-md-8">.col-md-8</div>
    <div class="col-md-4">.col-md-4</div>


Primer’s grid system is also flexible but more focused on GitHub’s specific design requirements. It uses a combination of flex utilities and a 12-column grid to achieve responsive layouts. Primer’s grid is less prescriptive, giving developers more control over the exact behavior of the grid on different screen sizes.

<div class="d-flex flex-wrap">
  <div class="col-8">.col-8</div>
  <div class="col-4">.col-4</div>

Components and Utilities


Bootstrap comes with a wide array of pre-styled components like buttons, navigation bars, modals, and cards. It also includes a host of utilities for spacing, sizing, and text alignment, which can be applied directly to HTML elements.

<button class="btn btn-primary">Primary Button</button>


Primer offers a more limited set of components, reflecting GitHub’s design language. While it includes utilities for spacing, color, and typography, the focus is on semantic class names that align with the design system’s principles.

<button class="btn btn-primary">Primary Button</button>



Bootstrap is highly customizable through Sass variables, mixins, and functions. You can easily create a custom build of Bootstrap by modifying the source Sass files before compiling the CSS.


Primer also allows customization via Sass, but its variables and mixins are designed to maintain consistency with GitHub’s design ethos. Customization is possible, but the framework encourages adherence to its design constraints.

JavaScript Components


Bootstrap includes a range of JavaScript plugins that provide additional functionality to components like modals, dropdowns, and tooltips. These plugins can be included via CDN or bundled with build tools like Webpack.


Primer does not come with JavaScript components out of the box. Instead, it focuses on the styling aspect of components, with the expectation that functionality will be implemented separately or by using Primer Components for React.


Both Bootstrap and Primer offer robust solutions for building web interfaces, but they cater to different needs. Bootstrap’s extensive list of components, utilities, and JavaScript plugins makes it a one-stop-shop for many developers, while Primer’s more constrained and semantic approach is tailored to creating interfaces that align closely with GitHub’s design philosophy.

In the next section, we will delve deeper into the themes and customization options, performance considerations, community and support, and real-world use cases for each framework. Stay tuned for more insights into Bootstrap vs Primer.

Themes and Customization Options


Bootstrap’s theming capabilities are one of its strong suits. It allows developers to extensively customize the look and feel of their site. The framework uses Sass, which provides variables for colors, fonts, and other UI elements that can be easily overridden.

Here’s an example of how you can customize Bootstrap’s Sass variables:

// Custom.scss
// Import Bootstrap's functions and variables
@import "node_modules/bootstrap/scss/functions";
@import "node_modules/bootstrap/scss/variables";

// Override the primary color
$theme-colors: (
  "primary": #5562eb,
  // Specify other color overrides here...

// Import the rest of Bootstrap
@import "node_modules/bootstrap/scss/bootstrap";


Primer also supports theming through Sass variables. However, the framework is more opinionated, and theming changes should align with the design principles laid out by GitHub’s design system. Customization is encouraged at a more granular level, with careful consideration for consistency and accessibility.

Here’s an example of customizing Primer:

// Custom.scss
// Import Primer CSS's variables and mixins
@import "primer-css/index.scss";

// Override the primary color
$blue: #0366d6; // GitHub's blue
$colors: (
  "blue": $blue,
  // Specify other color overrides here...

// Import the rest of Primer
@import "primer-css/index.scss";

Performance Considerations


Bootstrap is a relatively heavy framework due to its comprehensive list of components and JavaScript plugins. However, it offers a custom build option where you can select only the features you need, which can significantly reduce the file size and improve performance.


Primer is generally lighter than Bootstrap because it doesn’t include JavaScript plugins and has fewer components. This can lead to faster load times and better performance, especially in projects where a leaner, more focused framework is desired.

Community and Support


Bootstrap has a large and active community. It’s one of the most starred projects on GitHub and has extensive documentation, tutorials, and third-party resources available. This widespread adoption means that finding solutions to problems or hiring developers familiar with the framework is relatively easy.


Primer, while popular among developers who appreciate GitHub’s design system, has a smaller community compared to Bootstrap. However, it is well-documented and maintained by GitHub, ensuring reliable support and regular updates. The community may be smaller, but it’s also very focused on the Primer-specific design philosophy.

Real-World Use Cases


Bootstrap is versatile and can be used for a wide range of projects, from small personal websites to large-scale commercial sites. It’s particularly beneficial for rapid prototyping and MVP development due to its extensive pre-styled components.

Code Sample for a Bootstrap Navbar:

<nav class="navbar navbar-expand-lg navbar-light bg-light">
  <a class="navbar-brand" href="#">Navbar</a>
  <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNav" aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  <div class="collapse navbar-collapse" id="navbarNav">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      <!-- More nav items -->


Primer is ideal for projects that aim to have a clean, modern, and consistent design language similar to GitHub. It’s also a good choice for enterprise applications where design consistency and adherence to a specific set of principles are more important than a wide variety of UI components.

Code Sample for a Primer Button:

<button class="btn btn-primary" type="button">Primary button</button>


When deciding between Bootstrap and Primer, consider the scope and goals of your project. Bootstrap offers a broad range of possibilities and is a great choice for developers looking for a comprehensive, customizable, and widely-supported framework. On the other hand, Primer is perfect for projects that require a more refined and consistent design system, particularly if you’re looking to align with GitHub’s interface.

Both frameworks have their strengths and ideal use cases, and your choice should be guided by the specific needs of your project and the preferences of your development team. Whether you choose Bootstrap’s flexibility and community support or Primer’s design consistency and performance, both frameworks provide a solid foundation for building beautiful, responsive web applications.

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